Despite its name, the One-sided Bottlebrush doesn’t look like a household bottlebrush.
Bottlebrushes are much loved Australian wildflowers, with an easily recognizable cylindrical brush-like flower that gives the plant its name. The most common species is Red or Crimson Bottlebrush, Callistemon citrinus, which is native to the eastern states, but has been widely planted in the other states.
There are about 45 species of bottlebrush in the Callistemon family (or more accurately, genus). However, there is another whole genus of about 40 bottlebrushes, known as Calothamnus and native to the southwest of Western Australia. Callistemon and Calothamnus are both part of the Myrtaceae family, but they have some easily visible differences.
To see these differences, you simply have to look at the One-sided Bottlebrush, Calothamnus quadrifidus, which is common in bushland around Perth and the southwest of WA. As its common name suggests, the flowers of this plant mainly lie along one side of the stem. So it isn’t cylindrical like a household bottlebrush at all. A second point of difference is that the red spikes making up the One-sided Bottlebrush flower are curved and branched, whereas those on Callistemon species are straight, unbranched filaments.
In both cases, the red filaments are actually the stamens (male parts) of the flower. The petals are so small that you hardly notice them. The stamens of Calothamnus species, including the One-sided Bottlebrush, are often described as bundles or more evocatively as claws. Each flower head is made up of the stamens of many individual flowers, and is called an inflorescence by botanists.
You will easily spot One-sided Bottlebrush when walking through the bush in WA from mid-winter through to early summer, since the plant is colourful and distinctive. Even when the plant isn’t in flower, its needle-like leaves can be quite pretty. When the new shoots are growing, they are typically very colourful, with striking orange, red or mauve tinged leaves. The shrub often grows in a compact rounded shape, up to few metres in both height and width, but can also be found in a more spreading or straggly form.
The genus name Calothamnus means beautiful shrub in Greek (kalos thamnos), and the species name quadrifidus refers to the fact that the flower is divided into four parts, as you can see most clearly in the small buds, before they open. The species was named by Robert Brown, a botanist who travelled with Matthew Flinders on HMS Investigator. He collected a specimen of the plant, plus several other Calothamnus species, at Lucky Bay near Esperance on the south coast of WA, in 1802.
Going to Seed
As with most other bottlebrush species, the One-sided Bottlebrush has interesting seed pods. They develop as the flowers die, and form a tight cluster of capsules joined directly onto the branch stems. The pods are initially formed as small, fleshy, green fruit, which gradually dry out, turning grey-brown and woody as they mature.
The pods reportedly release their seeds after several years, but the empty pods remain on the plant for much longer, maybe even for life. Consequently, you are looking into the shrub’s past as you look from the outside towards the centre. There are new leaves and shoots on the outside, then the red flowers a bit further inside, followed by the most recently formed green fruit below the flower, and the old seed pods even further down the branches.
The flowers of One-sided Bottlebrush attract plenty of birds, and are especially popular with honeyeaters. They were also sucked by Aboriginal people to get the nectar, or soaked in water to produce a sweet nectar drink.
Where To Find Them
One-sided Bottlebrush grows in the southwest corner of Western Australia, from about Shark Bay to Israelite Bay and out into the goldfields as far as Norseman. It is widely distributed within this region and grows in many different soil types, though it is especially common on sand, gravel, limestone and granite outcrops. Its conservation status is classified as “Not threatened”.
In Perth, you will find the plant growing along bush trails in both Kings Park and Bold Park, and also in many small patches of remnant bushland. It is most noticeable from about June to December, when its red flowers make the shrub stand out among other native plants.
Since One-sided Bottlebrush is both pretty and fairly hardy, it has also been used as a horticultural plant. So you may see it planted in native gardens, including those outside its normal range.
For more information about One-sided Bottlebrush, visit www.florabase.dpaw.wa.gov.au/browse/profile/5426